More robust theme autoreload

[ilyaZar]

First, I appreciate if you find time to help me out on this, and I fully understand if that takes a bit more time !

The problem: it seems that theme auto-reload does not work consistently, as implemented by my PR #28

For my machine it works, otherwise I wouldnt have filed #28. Yet it does not work here basecamp/omarchy#5589

@kitlangton , if you find time, what would be yr take on the changes I propose here? I find it difficult to assess the nature of (a possible) race conditions if different machines/OS platforms send a sigusr2 signal and how to deal with that

I try to follow the same opentui path used in opencode’s tuitheme handling, which I roughly understand as:

opencode "pre-warms" he terminal palette and waits for theme mode before mounting some theme provider; then rsolves the system theme from renderer.getPalette({ size: 16 }) ; also clears opentui’s palette cache before rresolving system theme colors

Thats the files i looked at:

opencode/src/cli/cmd/tui/app.tsx
opencode/src/cli/cmd/tui/context/theme.tsx

The idea of the change here keeps ghui’s simpler SIGUSR2 mechanism from #28, but makes that path stricter: clear the cached palette before reads, wait for terminal to settle, retry palette reads, avoid replacing the current system theme when opentui/terminal justreturns incomplete palette data

does that make sense roughly ?